Rough engine sound

i began hearing a buzzing sound from what i think is the engine compartment. its a 2001 eclipse GT with sportronic transmission. the sound just began when the temperature dropped. the car is in great shape with 80k miles and has never had any problems with ownership. the buzzing sound is noticible and rough when you accelerate from 3k rpm and up. when driving sportonic in 4th gear and keep in 4th then accelerate, thats when its most noticible. also, i've been putting 93 octane as opposed to 87 in regularly. i know the car demands 93 but why would this began coincidently? i cant tell if its in the dash or engine compartment........if anyone has any advice to offer, it would be greatly appreciated

What weight motor oil are you putting in it? Depending on where you live, it might be a good idea to change to a lighter weight oil for cold weather (I use 10W30 in the summer, and 5W30 after September. I live in Nebraska and winter can suck ass). My car sounds like shit when its real cold out until it warms up, and it runs like hell, everything just slugs around until she has some heat in her.

cold weather is not a cars best friend. definitely change to 5-30 if it gets noticeably cold.

if you have been putting 87 in it before, i'd go ahead and unplug the ecu, and wait 15 min. then plug it back in. just to make sure the ecu recognizes you aren't putting crappy fuel in it.